Scientific measurements

Accuracy and Precision

• Accuracy refers to the closeness of measurements to the correct or accepted value of the quantity measured

• Precision refers to the closeness of a set of measurements of the same quantity made the same way

Percentage Error

Percentage error tells us by what percentage we are off from the accepted value of a quantity. The value is negative if the measured value is too small. It's positive if the measured value is too large.

Fill in the Blank

A student calculates the density of a substance as $$1.40\ \frac{g}{mL}$$ . The accepted value of the density is  $$1.30\ \frac{g}{mL}$$ . What is the percentage error of the student's measurement to the tenth's place?

Rounding Rules:

• If the number is 4 or less, then the current number stays (i.e. Rounding 1.44 to the tenth's place is 1.4)

• If the number is 5 or greater, the number rounds up (i.e. Rounding 9.725 to the hundredth's place makes the number 9.73)

Fill in the Blank

Round 912 to the hundred's place.

Fill in the Blank

Round 21.95 to the tenth's place.

Scientific Notation is a shorthand method of writing incredibly large and incredibly small numbers

• The integer (often represented by M) must be between 1 and 10.

• If the power of 10 (often represented by n) is negative, the number is incredibly small. If it is positive, then it is incredibly large.

The digit to the left of the decimal point must be between 1 and 10 (or, a nonzero digit)

Count each space the decimal moves and that is the power of ten. If it moves to the right, it is negative (or subtracts one from n). If it moves to the left, then it is positive (or adds one to n).

Scientific Notation Operations

Addition and Subtraction

Multiplication and Division

​The SI System Uses Metric

• The Metric System: a standard measurement system based on the number 10

  • Allows scientists to compare data and communicate with each other

  • Uses different units for different types of measurements

    • Meter

    • Liter

    • Gram

  • Prefixes tell you how many of each unit there are

Grade 8 Science Ohio | Lesson 2.1

Grade 8 Science Ohio | Lesson 2.1

Fill in the Blank

How many meters are in a Kilometer

Fill in the Blank

How many centimeters are in a meter

​Length

• Length: the distance from one point to another

  • Base Unit is the meter

    • 1 meter=100 centimeters

    • 1000meters= 1 kilometer

Grade 8 Science Ohio | Lesson 2.1

Fill in the Blank

How many meters are in a dekameter

Reorder

Rank the prefixes from largest to smallest

• Kilo-

• Hecta-

• deci-

• centi-

• milli-

1

2

3

4

5

• 1
• 2
• 3
• 4
• 5

Mass Vs. Weight

• Mass: the amount of matter within an object

  • Unless you do something to change an object, it's mass doesn't change​

    • We tend to measure in Kilograms in the metric system

      • Small objects use grams

• Weight: The force of gravity acting on an object

  • SI base unit is the Newton

  • Can change depending where you are in the universe

Grade 8 Science Ohio | Lesson 2.1

Fill in the Blank

A picnic blanket is 1 meter across. and ant is 1 centimeter in length. How many ants would fit end to end across the picnic blanket?

Fill in the Blank

nickel weighs 5 grams. How many milligrams does it weigh?

​Volume

• Volume: the amount of space an object takes up

  • For regular shapes :Calculated by multiplying Length x Width x Height

  • For Irregular Shapes: Calculated in a lab using a displacement method

  • Units include

    • Centimeters Cubed: cm³

    • Meters Cubed: m³

    • Liters: L

Grade 8 Science Ohio | Lesson 2.1